The circulation pumps employed in devices through which water flows, particularly for conveying washing water in dishwashers used in households or in industry, are normally centrifugal pumps which are mounted at the bottom of the washing tub. Such a pump serves to circulate the washing solution by pumping it out of the washing tub and then back into it again through the spray arms of the system and over the items to be washed. In this context, for purposes of achieving economical and energy-saving operation, it is a generally known procedure to regulate the feed of washing solution to the spray arms as a function of the load in the dish rack in the washing tub and/or as a function of the program set for the type of items to be cleaned. Thus, for instance, it is common practice for the washing or cleaning solution that is circulated by the dishwasher's built-in circulation pump to be alternately fed to the spray arms associated with the dish racks or else for certain spray arms to be disconnected from the supply of washing water, for instance, the lower spray arm when the lower rack is not loaded.
Switching to one spray arm or another or else completely closing the water conduits in the washing system is regulated in a known manner as a function of a program by a so-called water diverter (see German utility model DE 88 16 597 U1) located downstream from the delivery side of the circulation pump.
In the case of a circulation pump that has only one discharge port that branches off to the upper and the lower spray arm feed lines downstream from the pump, it is common practice to arrange the water diverter in the branching-off point so that the water diverter then supplies either the upper, the lower or else both spray arms with washing solution as a function of the cleaning program that has been pre-selected. If there are, for example, three or more spray arms of which at least one is always supposed to be supplied with washing solution, then the water diverter can also be arranged in a branched-off spray arm feed line as an additionally switchable line branch.
Moreover, German utility model DE 75 14 342 U1 discloses a pump that is connected via its discharge ports to hydraulic aggregates such as, for example, a control cylinder, a venting mechanism, an admixer, etc. A shut-off device is provided so that the connected aggregates can be switched off. The shut-off device has plate-like blocking elements that are affixed to a bracket. The bracket with its blocking elements is arranged in the pump chamber and can be moved in the circumferential direction by means of a manual lever provided outside of the pump in order to close or open the discharge ports, whereby the blocking elements are arranged in such a way that either all of the discharge ports are open or all of them are closed.
DE 211 4978 describes a pump having blocking elements arranged in its pump chamber, said elements being connected to each other by means of a bracket. The blocking elements, preferably two, are each located upstream from a discharge port provided on the circumference. By means of a rod, which is connected to a blocking element and which protrudes from a bore in the pump housing, the blocking element can be pushed into the pump chamber so that the corresponding discharge port can be opened, while the blocking element closes off the corresponding discharge port on the other side of the bracket.